1. Field of the Invention
This invention concerns devices and methods for specifying and applying magnetic fields, and more particularly to such devices and methods useful in the field of stereotactic surgery in which a magnetic delivery vehicle such as a magnetically-tipped catheter or endoscope, or a magnetic seed of another type is used.
2. Description of the Related Art
It is known in the art to provide magnetic manipulation of diagnostic or therapeutic elements (which, for simplicity, we shall herein refer to collectively as "magnetic delivery vehicles") through body tissue or ducts (such as in vascular exploration or treatment). Systems providing for such manipulation are described in a number of previously published articles and patents, such as "Magnetically Guided Devices for Vascular Exploration and Treatment," Sadek K. Hilal et al., Radiology 113, 529-540 (1974); U.S. Pat. No. 3,358,676, entitled "Magnetic Propulsion of Diagnostic or Therapeutic Elements Through the Body Ducts of Animals or Human Patients," issued Dec. 19, 1967 to Ephraim H. Frei et al.; "Magnetic Manipulation Instrumentation for Medical Physics Research," George T. Gillies et al., Review of Scientific Instruments 65, 533-562 (1994); "Characteristics of an Improved Magnetic-Implant Guidance System," Robert G. McNeil et al., IEEE Trans. on Bio. Eng. 42(8) 802-808 (1995); "Functional Design Features and Initial Performance Characteristics of a Magnetic- Implant Guidance System for Stereotactic Neurosurgery," Robert G. McNeil et al., IEEE Trans. on Bio. Eng. 42(8) 793-801 (1995); and U.S. Pat. No. 5,654,864 to Ritter et al., entitled "Control Method for Magnetic Stereotaxis System," issued Aug. 5, 1997. All of these references are hereby incorporated in their entirety by reference.
The cited systems all provide fixed or manually moved or controlled permanent magnets or electromagnets that are capable of applying fields and forces to treatment implants to move or guide the implant through a treatment region. These systems require manual control by a technician in accordance with the instructions of a surgeon during an operating procedure, or by the surgeon himself or herself. It would be desirable to provide a device and a method to simplify the control of the application of magnetic fields to a magnetic delivery vehicle implanted in a patient, so that a surgeon can simply observe a current location of the magnetic delivery vehicle and specify, in an intuitive manner, the next desired location and have magnetic fields applied in a proper orientation to guide, push, or pull (as the case may be) the magnetic delivery vehicle to the next location. It would be particularly useful to provide a surgeon with a device and method for specifying a three-dimensional path for the magnetic delivery vehicle.